1. Field of the Invention
The present invention relates to an automobile muffler, and more particularly to an automobile muffler which is capable of draining water from the sound-deadening space defined between its exhaust and outer pipes, thus assuring that no water remains in the sound-deadening space.
2. Description of the Prior Art
As is well known, a conventional automobile muffler comprises outer and inner or exhaust pipes defining the sound-deadening space therebetween, the sound-deadening space being filled with sound-deadening material. While the automobile muffler is used, water is accumulated in the sound-deadening space for the following reasons: the exhaust gas at an elevated temperature flows from the engine to the muffler to raise the temperature of the muffler. Accordingly the air within the muffler is heated and expanded. Then, assume that the car stops and its engine stops. Then, no exhaust gas of elevated temperature flows into the muffler, and therefore the temperature of the muffler decreases soon. Accordingly, the temperature of the air within the muffler decreases sharply, and hence the volume of the air within the muffler decreases sharply, therby drawing air from the open end of the muffler from the surrounding atmosphere. Specifically, air is drawn from the open end of the exhaust pipe, passing through the apertures of the exhaust pipe to enter the sound-deadening space within the surrounding outer pipe. The moisture content when heated, rises to the upper area of the sound-deadening space, which still remains at an elevated temperature.
The moisture is accumulated there because no drain is provided. As the sound-deadening space cools down, the moisture reduces to water, and the water descends to the lower area of the sound-deadening space, and is held there. The accumulation of water in the sound-deadening space of the muffler will have an adverse effect on sound-deadening. Also disadvantageously, the accumulated water will be scattered from the open end of the muffler when the engine starts, and the sputtering water fouls the surrounding. In an attempt to solve such problems it has been proposed that a drain cock is provided to the bottom of the outer pipe, thereby permitting the water to be drawn out of the sound-deadening space of the muffler. However, a person must craul on the back under the automobile chassis to open the drain cock, and this is no easy work.
In an attempt to solve this problem an automobile muffler as shown in FIGS. 8 and 9 is proposed. As shown, its outer pipe 1' is equipped with a drain pipe 2', one end 3' of which is put in the lower area y' of the sound-deadening space 4' of the muffler, thereby permitting the accumulated water 5' to flow out of the outer pipe 1' via the drain pipe 2'. This automobile muffler, however, has following defects: (a) it cannot prevent condensation of moisture to water in the upper area of the sound-deadening space 4' of the muffler (it is difficult to remove the water from the sound-deadening space 4' because the water is caught between the narrow inter-spaces of filament like sound-deadening material); and (b) the water descends by gravity all the time, and therefore water is accumulated in the lower area of the sound-deadening space. In the past, effort was directed to remove water from the lower area of the sound-deadening space of the muffler.